Abstract
Recent research has suggested that the discharge rate of traffic across the stop-line of signalised intersections is not constant (a conventional assumption when deriving saturation flow), but varies over the green time. Different studies have shown very different patterns of variation, but the reasons for these differences have not been fully explained. This study firstly compares previous results studying this variability and then attempts to explain why different patterns were produced by different situations. Then, another study is undertaken in traffic dominated by motorcycles also presented. It appears that the pattern of the discharge rate at signalised intersections depends on degree of saturation, traffic composition and types of signal control. Furthermore, it also seems that built-up time of discharge rate depends much on the proportion and manoeuvrability of the predominant type of vehicles at the head of the queue. Finally, the impacts of these unconventional patterns on the optimisation of signal timings are discussed through a practical example.
